Shading ring induction motor



March 5, 1935. E. D. LILJA 1,992,956

` SHDING RING' INDUCTION MOTOR Filed oct. 27, 1952 las@ lll! W I .l E"

INVENTOR Edgar D. Lilja 6 ATTORNEYS 3 SYMPA/1.5%

Patented 4lVlar.l 5, 1,935 I v s PATENT OFFICE 1,992,956, sIrADING .RING INDUCTION Moron Edgar D. Lilj'a, Rockford, Ill., assignor to Howard D. Colman, Rockford, Ill.

Application october 27, i932, serial No. 639,760 t 14 claims. -(01. 17a-27s) rIhis invention relates to shading ring induca spool 11 abutting at one end against right angle tion motors and more particularly to those havportions 12 of the legs 8. For the sake of coming stators of the so called shell type in which pactness where only one exciting winding is emthe iron of the field member encloses the exciting ployed, the opposite ends of theA legs may be 5 Winding and provides at least two available magcurved toward the end 13 of the member 6 which 51 netic circuits for the flux-set up by excitation latter end may be relatively shorter than the UNITED STATE `of the winding, core and need not be yformed with parallel In motors of the aboveclass heretofore consides. structed, the shading ring for each pole is mount- To permit each lamination to be formed in one 10 -ed on the magnetic core of the exciting winding integral piece and allow for convenient assem- 10 closely adjacent the latter. In this position, the bly of the same and the winding 9, each lamiring is closely coupled magnetically withthe nation is severed at the end of the corev 10 to winding so as to cause transformer and short cirpermit the member A6 as a whole to be exed cuit losses of such magnitude as to impair maaway -from the legs 12 and the core to be in- 15 -terially the efficiency of the motor and to preserted through the s13001- Thev required degree 15 vent the use of shading ringshaving `electrical of ilexing is permitted in view of the length o! characteristics which will produce optimum perthe member 6. If desireda lap joint may be formance. formed by severing thelaminations alternately The primary object of the invention is to overalong lines 14 and 15. l

come the defect in prior shell type motors by a A rotor 16 of the squirrel cage type `is mounted 20 novel construction of the motor poles and arin the recess '7' with its shaft 17 journaled at oprangement of the shading rings thereon remote poste ends in bearing plates 18 rigidly secured from the exciting winding. i at opposite ends to the assembled stator.

The invention also resides'in the novel man- In order that the shading rings by which the g5 nerA of defining the desired spaced relation of magnetic field is caused to rotate -around the .ro- 25 the motor poles and the differently shaded face tor recess may be located remotely from and areas thereof. out of closely coupled relation to the winding 9 .Other objects and advantages of the invention as contemplated by lthe present invention, the will becomeapparent from the following detailed magnetic poles are constructed to permit locadescription taken in connection with the accomtion of the shading rings in positions spaced sub- 30 panying drawing; in which c 1 stantial distances around the rotor from the po- Figurel is a -perspective view of a motor emsitions normally occupied by the rings in shell bodying the features of the present invention, a type motors. To this end, the iron portion of vportion of the bearing frame being broken away. the member 6 between the winding `9 and the rov Fig. 2 is 'an elevational view with the field tor forms only a part of the unshaded portionof 35 'winding shown in section. one pole, the center of the shaded portion being -Fig. 3 is a perspective view of one of the stator shifted around the rotor and disposed beyond laminations. l a diameter 19 of the rotor perpendicular to the v Figs. 4 and 5 are views similar to Fig. 2 showaxisof the winding 9. This arrangement is at- 0 ing modified forms of the motor. tained by bulging the intermediate portion of 40 The motors shown in the drawing by way of the member 6 outwardly in opposite directionsV illustration are of the two pole type, each havingA from the rends 10 and 13 forming laterally offset a laminated stator preferably comprising an inextensions 20 and 21 of these ends each project- 5 tegral elongated magnetic' member designated ing around-the rotor to a p oint adjacent the opgenerally by the numeral V6 and constituting the positeend 10'or l13 of the member 6. The ex- 45 rotor leg and also the winding leg of the stator. tensions 20 and 21 are of substantial'radial width Near its center the member is yformed with a and at their ends preferably taper to narrow magcylindrical rotor recess 'l and its opposite endsYI netic restrictions 22 formed by inwardly conv .are magnetically -joined by somewhat narrower `verging notches 23 extending laterally into the 5 legs 8 each spaced from the member 6 and comember 6 toward the rotor recess. i 5o operating therewith to form a magnetic circuit It will be apparent that the end 10 and the exaround one or more main field windings 9 entension 20 thereof and the end 13 and the extencircling the member. In the -forms shown in sion 21 thereof constitute two pole projections Figs. 1 to 4, thehend 10 of the'member 6 forms with substantially alined ends onopposite`sides u thecore for-the winding 9 which is carried by of the rotor and inner endsextending beyond 55 rotor between them, each extension being integrally connected Ato the other by one of the restrictions 22. The rotor surface is thus completely enelosedby two substantially continuous faces disposed on opposite sides of a diameter of the rotor through the restrictions 22.

While only one shading ring need be employed on each pole, two rings numbered 24 and 25 are used hereinboth being mounted on the extensions 20 and 21 adjacent the diameter 19 and therefore areA disposed remotely from the Winding 9 and the ends-10 and 13 of the member 6. In the present instance, the larger rings 24 are disposed between the diameter 19 and the ends 10k and 13 and extend through short slots 26 in the extensions y20 and 21 adjacent and opening into the rotor recess. The smaller rings are disposed `on the opposite side of the diameter 19 extending through relatively longer slots 27 in the case of the motor shown in Fig. 2.

From the foregoing it will be apparent that the iron of each pole is" divided into an unshaded section a section y shaded by the ring 24, and a section z shaded by both rings, each pole iace being dividedby the slots 26 and 27 into unshaded, single shaded, anddouble shaded areas 28, 29 and 30.

The relative sizes of the differently shaded areas are determined by the location of the slots 26 and 27 and the relative sizes oi the single and double shaded iron sections y and e are determined by tlie spacing of the slots. With the pole projections constructed and the shading rings arranged thereon as above described, it will be apparent that the correspondingly shaded areas of the two poles are o1 the same size and are diametrically opposite each other and are thus adapted to produce proper space displacement of the rotating field components. Proper phase displacement between the iield components threading each pole is obtained through the use of shading rings of suitable low resistance.

The winding 9 is designed to cause substantial saturation of the stator iron when excited by alternating current. The major portion oi the' dux thus set 'up threads the rotor, the unshaded pole sections 28, and the legs 8 along vpaths indicated by dotted lines 31 (Fig. 2)'. A

portion of the flux-diverted around the extensions 20 and 21 threads the rings 24 causing currents to be inducedin the latter, which currents set up a magnetic held reacting with the main field to produce a lagging of the resultant flux which threads the rotor from the sections y. Owing to the location of these sections which are defined by the slots 25 and 27, this lagging iiux enters the rotor substantially at right angies to the axis ofthe winding 9. In a `similar way, currents are induced in the rings 25 by the :tlm: threading the latter with the result that the linx threading the pole sections z between the notches 23 and the slots 27 is displaced in time phase still farther from the unshaded ilux. The magnetic field thus shifts progressively across the pole races.

In the arrangement above described, it will be' apparent that the shading rings of the poles are 1,992,956 each other in nierauy onset relation with the the result that the transformer and short circuit losses are reduced to a minimum. Accordinglyv the efii'ciency ofthe motor is materiallydncreased and the shading rings may be formed of the low resistance which is necessary .in order to produce a magnetic eld of maximum effectiveness.

It will be apparent from the foregoing that the pole projections may take various shapes. As shown for example in Fig. 4, the taper of the projections 20 and 21 may extend substantially throughout their lengths and the slots 26 and 27 made of the same length.

Fig. 5 shows a modification of the motor in which two windings 9 are employed, the second one having a core formed by the end 13 of the magnetic member. To permit assembly of the laminations when two `windings are used, the stator is formed in two pieces, the member 6 constituting one of these, the other being formed by the rectangle composed of the legs 8, l2 and 34 and magnetically connecting opposite ends of the member 6 externally of the windings 9. To form lap joints at opposite ends of the member 6, the alternate laminations are severed along lines 32 and 33.

I claim as my invention:

1. A motor of the character described combining an integral elongated member with magnetically connected opposite ends and forming two pole pieces with faces defining a cylindrical rotor recess formed intermediate the ends of the member, a rotor in said recess, a field winding enclosing one end of said member, a notch extending laterally into said member between said winding and said rotor, said notch converging inwardly and terminating adjacent but short ci' said recess, a similar notch in said member diametrically opposite said ilrst notch and cooperating therewith to define said pole pieces, a shading coil enclosing a section of one'of said pole pieces and disposed approximately midway between said winding and the notch at the opposite end of said member, and a shading coil on said other pole piece diametrically opposite said rotor irom said first mentioned shading coil.

2. A motor oi the character described combining an elongated magnetic member having a cylindrical recess therein intermediate its ends and inwardly converging lateral notches on opposite sides thereoi terminating adjacent vbut short of said recess whereby to deiine two magnetic'pole pieces disposed on diametrically opposite sides oi said recess with adjacent side tips integrally connected at the roots of said notches, a field winding enclosing one end of said member, two magnetic'connections joining opposite ends oi said memberand enclosing said winding, a rotor rotatable in said recess, and two shading rings, one on each of said pole pieces disposed substantially diametrically opposite each other and substantially equidistant i'rom the ends oi' said member.

3. A motor of the character described combining a rotor, two magnetic members extending toward said rotor with their adjacent ends laterally oiiset and each extending around the rotor nections joining the outer ends of said members externally of said winding.

4. A motor of the character described combining a cylindrical rotor, amagnetic member hav` ing a straight sided portion at one end extending toward said rotor and a curved sided portion at the other end. defining a pole face partially enclosing the periphery of said rotor, a field winding enclosing said straight sided portion, a shading ring enclosing said curved sided portion and spaced from said winding whereby to shade the side portion of said face remote from the winding, a second member providing a pole face on the side of said rotor opposite said first mentioned face; a short-circuited ring on the latter member shading -a corresponding side portion of the latter face, and magnetic connections joining the outer ends of said members.

5. A motor of the character described combining a rotor, a field winding arranged with its axis extending toward said rotor, two polar members extending toward said rotor from opposite sides thereof and one constituting lthe core of said winding, the inner adjacent ends of said members following around the rotor surfaces and defining pole faces extending beyond a diameter of the rotor parallel to said winding, shading means on said inner ends spaced from said winding and acting to cause lagging flux to enter the rotor from each pole face beyond said diameter, and magnetic connections extending around said winding and joining the outermost ends of said members.

6. A motor of the character described com bining a rotor, two magnetic members extending toward the rotor on opposite sides thereof with their inner adjacent ends laterally offset with respect'to each other and extending around the rotor surface, a field winding on one of said members, shading coils enclosing sections of said inner ends and disposed on opposite sides of the rotor adjacent a diameter perpendicular ,to the axis of said winding, and means magnetically joining the outermost ends of said members'and extending around said winding.

'1. A motor of the character described com bining a rotor, a field winding arranged with its 'axis extending toward said rotor, an elongated magnetic member providinga core for said winding and also two pole pieces having faces substantially enclosing and disposed on opposite sides of said rotor, short-circuited coils spaced rem motely from said winding and core and positioned to cause lagging flux to thread the ro'tor from porf tions of said faces disposed opposite each other substantially along a diameter perpendicular to the axis of said winding, the portions of said faces along a diameter generally parallel to said axis being unshaded, and means magnetically connecting opposite ends of said member and enclosing said windingl 8.v A motor of the character described combining a rotor, a field winding, a magnetic cor'e for said winding projecting toward said rotor and forming an unshaded vpole face area, a laterally offset magnetic extension integral with said core and extending partially around said rotor from said core'to form a lcontinuation of said area, a shading ring on said extension` and acting to cause a lagging of the fiux` entering a portion of the rotor periphery, the major portion of such laggingk flux entering the rotor beyond a diameter of the rotor perpendicular tothe axis of said winding, a magnetic polar projection with a shadingring thereon providing unshaded and shaded face areas diametrically opposite the corresponding areas of said first mentioned face, and means magnetically connecting said core and projection externally of said winding and said extension.

9. A motor of the character described combining a rotor, a field winding, a magnetic core for said winding projecting toward said rotor and forming an unshaded pole face area, a'laterally offset magnetic extension integral with said 'core and extending partially around said rotor from said core to form a continuation of said area, a short-circuited coil projecting through said extension and defining a shaded portion of said face area, the center of said portion being located beyond a diameter of the rotor perpendicular to the longitudinal axis of said core, a magnetic polar projection with a shading ring thereon .providing unshaded and shaded face areas diametrically opposite the corresponding yareas of said first mentioned face, and means magnetically connecting said core and projection externally of said winding and said extension.

10. A motor `oi? the character described combining a rotor, two magnetic members disposed on opposite sides of said rotor and havinglaterally offset inner ends each extending around said rotor to a point adjacent the other member,

a field winding around one of said members,

vshading coils on said inner ends spaced from said winding and acting to cause lagging flux to enter the rotor from the faces beyond the coils, and means magnetically joining the outermost ends of said members externally of said winding. l 11. A motor of the character described combining a rotor, a pair of field windings arranged on opposite sides of said rotor with their axes extending in the same vgeneral direction, two

'magnetic members having their outermost ends enclosed by said windings and their adjacent ends bulging outwardly around said rotor between said windings, there being a magnetic restriction at the innermost end of each member adjacent the winding of the other member, shading rings near said inner ends located approximately midway between said windings and acting to cause a lagging flux to enter the rotor from each member over the area between its ring and the adjacent restriction, and means magnetically joining said members externally of said windings.

12. For a motor of the character described, a single piece stator lamination comprising a member of generally rectangular shape and a cross-member integral at one end lwith one side of the rectangle and having its other end disposed adjacent but severed from the opposite side of the rectangle to permit fiexing of said cross-member and insertion thereof through a field winding, the intermediate portion of said cross member providing two pole pieces defining a rotor-recess and having opposite side tips integrally joined by connections of narrow radial width.

i3. A`motor of the character described comprising, in combination, a rotor, a plurality of pole pieces projecting toward said rotor in anshading coils one on each oi said extended side member, a field `Winding enclosing one o! said portions disposed remotely from and out of members, a shading ring for each member enfclosely coupled magnetic relation with respect to closing said extended side portion, each shading said windingwhereby to form shaded pole face ring being disposed remotely from and out of areas at the innermost end portions of said exclosely coupled relation with respect to said 5 tended side portions, and means magnetically winding and defining for each membera shaded connecting the remote ends oi' said pole pieces. pole face area the major portion of which is dis- 14. A motor of the character described composed beyond the median plane between one prising, in combination, a rotor, .a plurality oi.' memberand the unshaded side of the adjacent lo magnetic members projecting toward said rotor member,- and means magnetically connecting the 10 and having oneside portion closely following the remote ends oi.' said members.

rotor contour and extending around j the same toward the other side portion` of an adjacent t EDGAR D. LllJA. 

